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Specification Analysis of Option Pricing Models Based on Time‐Changed Lévy Processes

Journal of Finance 2004 59(3), 1405-1439 open access
We analyze the specifications of option pricing models based on time‐changed Lévy processes. We classify option pricing models based on the structure of the jump component in the underlying return process, the source of stochastic volatility, and the specification of the volatility process itself. Our estimation of a variety of model specifications indicates that to better capture the behavior of the S&P 500 index options, we need to incorporate a high frequency jump component in the return process and generate stochastic volatilities from two different sources, the jump component and the diffusion component.

The Global Credit Spread Puzzle

Journal of Finance 2025 80(1), 101-162
We examine the ability of structural models to predict credit spreads using global default data and security‐level credit spread data in eight developed economies. We find that two representative, pure default‐risk models tend to underpredict the average credit spreads on investment‐grade (IG) bonds, especially their spreads over government bonds, thereby providing evidence for a “global credit spread puzzle.” However, a model incorporating endogenous liquidity in the secondary debt market helps mitigate the puzzle. Furthermore, the model captures certain determinants of corporate bond market frictions across the eight economies and substantially improves the cross‐sectional fit of individual IG credit spreads.